A detailed description of an optical polarimetric scatterometer, its capabilities, and special application are presented. This instrument measures the 4×4 Mueller matrix elements as well as bidirectional reflective distribution functions (scatter cross sections) for light that is scattered from a target. Incident polarized light at wavelengths λ=0.6328 and λ=1.06 μm can be directed toward the target in an arbitrary direction. The receiver can be located anywhere in the solid angle 4π. Backscatter measurements, most commonly used in remote sensing, can also be obtained. The scatterometer has been used to validate different analytical/numerical solutions to a broad class of electromagnetic scattering problems, in controlled laboratory experiments. The optical constants of liquids and solids can be determined by relating the Mueller matrix elements to the ellipsometric parameters. Recently, the relationships between the Mueller matrix elements and the parameters related to the optical activity have been derived. Thus, the scatterometer has the potential to detect, identify, and characterize optical rotation and circular dichroism of biological and chemical materials that possess chiral properties. These relationships are based on depolarization of waves reflected and transmitted through optically active media. Only the eight quasi off-diagonal elements of the Mueller matrix are sensitive to optical activity.